8000 Fix bug in SymmetricalLogTransform. by efiring · Pull Request #14295 · matplotlib/matplotlib · GitHub
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Fix bug in SymmetricalLogTransform. #14295

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Merged
merged 4 commits into from
May 22, 2019
Merged

Fix bug in SymmetricalLogTransform. #14295

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d3ca16c
Fix bug in SymmetricalLogTransform.
efiring May 21, 2019
b218e7c
SymmetricalLogTransform and inverse return same type as input.
efiring May 22, 2019
e2c460e
Add a test for the transform and its inverse
efiring May 22, 2019
a904fab
Shorten a line.
efiring May 22, 2019
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38 changes: 16 additions & 22 deletions lib/matplotlib/scale.py
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Original file line number Diff line number Diff line change
Expand Up @@ -485,18 +485,14 @@ def __init__(self, base, linthresh, linscale):
self._log_base = np.log(base)

def transform_non_affine(self, a):
sign = np.sign(a)
masked = ma.masked_inside(a,
-self.linthresh,
self.linthresh,
copy=False)
log = sign * self.linthresh * (
self._linscale_adj +
ma.log(np.abs(masked) / self.linthresh) / self._log_base)
if masked.mask.any():
return ma.where(masked.mask, a * self._linscale_adj, log)
else:
return log
abs_a = np.abs(a)
with np.errstate(divide="ignore", invalid="ignore"):
out = np.sign(a) * self.linthresh * (
self._linscale_adj +
np.log(abs_a / self.linthresh) / self._log_base)
inside = abs_a <= self.linthresh
out[inside] = a[inside] * self._linscale_adj
return out

def inverted(self):
return InvertedSymmetricalLogTransform(self.base, self.linthresh,
Expand All @@ -519,16 +515,14 @@ def __init__(self, base, linthresh, linscale):
self._linscale_adj = (linscale / (1.0 - self.base ** -1))

def transform_non_affine(self, a):
sign = np.sign(a)
masked = ma.masked_inside(a, -self.invlinthresh,
self.invlinthresh, copy=False)
exp = sign * self.linthresh * (
ma.power(self.base, (sign * (masked / self.linthresh))
- self._linscale_adj))
if masked.mask.any():
return ma.where(masked.mask, a / self._linscale_adj, exp)
else:
return exp
abs_a = np.abs(a)
with np.errstate(divide="ignore", invalid="ignore"):
out = np.sign(a) * self.linthresh * (
np.power(self.base,
abs_a / self.linthresh - self._linscale_adj))
inside = abs_a <= self.invlinthresh
out[inside] = a[inside] / self._linscale_adj
return out

def inverted(self):
return SymmetricalLogTransform(self.base,
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31 changes: 30 additions & 1 deletion lib/matplotlib/tests/test_scale.py
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Original file line number Diff line number Diff line change
@@ -1,9 +1,11 @@
from matplotlib.cbook import MatplotlibDeprecationWarning
import matplotlib.pyplot as plt
from matplotlib.scale import Log10Transform, InvertedLog10Transform
from matplotlib.scale import (Log10Transform, InvertedLog10Transform,
SymmetricalLogTransform)
from matplotlib.testing.decorators import check_figures_equal, image_comparison

import numpy as np
from numpy.testing import assert_allclose
import io
import platform
import pytest
Expand All @@ -22,6 +24,33 @@ def test_log_scales(fig_test, fig_ref):
ax_ref.plot(xlim, [24.1, 24.1], 'b')


def test_symlog_mask_nan():
# Use a transform round-trip to verify that the forward and inverse
# transforms work, and that they respect nans and/or masking.
slt = SymmetricalLogTransform(10, 2, 1)
slti = slt.inverted()

x = np.arange(-1.5, 5, 0.5)
out = slti.transform_non_affine(slt.transform_non_affine(x))
assert_allclose(out, x)
assert type(out) == type(x)

x[4] = np.nan
out = slti.transform_non_affine(slt.transform_non_affine(x))
assert_allclose(out, x)
assert type(out) == type(x)

x = np.ma.array(x)
out = slti.transform_non_affine(slt.transform_non_affine(x))
assert_allclose(out, x)
assert type(out) == type(x)

x[3] = np.ma.masked
out = slti.transform_non_affine(slt.transform_non_affine(x))
assert_allclose(out, x)
assert type(out) == type(x)


@image_comparison(['logit_scales.png'], remove_text=True)
def test_logit_scales():
fig, ax = plt.subplots()
Expand Down
0